Significant improvements in animal performance, efficiency and carcass and meat quality have been made over the years through the application of standard animal breeding and selection techniques. However, such classical animal breeding techniques require several years of genetic evaluation of performance records on individual animals and their relatives and are therefore very expensive. Other efforts have been made to improve productivity and quality through the application of such management practices as the use of feed additives, animal hormonal implants and chemotherapeutics. However, there is significant political and regulatory resistance to the introduction and use of such methodologies. Such methodologies are also non-inheritable and need to be applied differently in every production system.
There is a need for methods that allow relatively easy and more efficient selection and breeding of farm animals with an advantage for an inheritable trait of circulating leptin levels, feed intake, growth rate, body weight, carcass merit and carcass composition. The economic significance of the use of genetic markers that are associated with specific economically important traits (especially traits with low heritability) in livestock through marker-assisted selection cannot therefore be over-emphasized.
The physiological regulation of intake, growth and energy partitioning in animals is under the control of multiple genes, which may be important candidates for unraveling the genetic variation in economically relevant traits (ERT) in beef production. Polymorphisms in these candidate genes that show association with specific ERT are useful quantitative trait nucleotides for marker-assisted selection. In the present study, associations between single nucleotide polymorphisms (SNPs) in the bovine growth hormone receptor (GHR), bovine neuropeptide Y (NPY), leptin, ghrelin and uncoupling protein 2 (UCP2) genes with measures of intake, growth and carcass merit in beef cattle.
The GHR is bound by GH in a homodimeric group resulting in the initiation of signal transduction mechanisms and the subsequent activation of many hormonal systems involved in growth promotion as well as lipid, nitrogen, mineral and carbohydrate metabolism. The interactions between GH and its receptor also affect protein synthesis, protein degradation, and regulation of overall protein turnover. Other areas of activity are effects on nitrogen retention, fat synthesis, fatty acid oxidation, and stimulation of fatty acid mobilization from body adipose tissues. Treatment of farm animals with growth hormone has been shown to lead to decreased feed intake, increased average daily gain, increased feed efficiency, decreased fat accretion and increased protein accretion.
Ghrelin is a growth hormone releasing peptide, consisting of 28-amino acids, which serves as an endogenous ligand for growth hormone-secretagogue (G-protein-coupled). These receptors in turn stimulate the release of GH from the pituitary gland. In addition, ghrelin has also been shown to play important roles in the stimulation of appetite and feeding activity through interactions with peptides such as NPY.
Leptin, the hormone product of the ob (obese) gene, has been shown to be predominantly synthesized and expressed in adipose tissues. It functions as a potent physiological signal in the regulation of body weight, energy expenditure, feed intake, adiposity, fertility and immune functions. Leptin has been proposed as one of the major control factors contributing to the phenotypic and genetic variation in the performance and efficiency of cattle.
Polymorphisms in the coding regions of the leptin gene in cattle have been associated with milk yield and composition (see, e.g., Liefers et al., J Dairy Sci. 2002 June; 85(6):1633-8), feed intake (see, e.g., Liefers et al., J Dairy Sci. 2002 June; 85(6):1633-8; Lagonigro et al., Anim Genet. 2003 October; 34(5):371-4), and body fat (see, e.g., Buchanan et al., Genet Sel Evol. 2002 January-February; 34(1):105-16; Lagonigro et al., Anim Genet. 2003 October; 34(5):371-4). Polymorphisms in the leptin promoter have been identified, specifically the UASMS1, UASMS2, UASMS3, E2JW, and E2FB SNPs (see, e.g., Nkrumah et al., J Anim Sci. 2005 January; 83(1):20-8; Schenkel et al., J Anim Sci. 2005 September; 83(9):2009-20) and the A59V SNP (see, e.g., Liefers et al., Mamm Genome. 2003 September; 14(9):657-63), however, only the UASM2 SNP (see, e.g., Nkrumah et al., J Anim Sci. 2005 January; 83(1):20-8) has been associated with serum leptin concentration and economically relevant traits of growth, feed intake, efficiency and carcass merit in cattle.
Neuropeptide Y is a 36-amino acid peptide that plays a powerful role as a central appetite stimulator playing important roles in the regulation and control of food intake and energy-balance. It stimulates food intake and induces a general anabolic state by reducing energy expenditure. Additionally, NPY influences the regulation of growth in animals by causing a dose-dependent inhibition of GH release, and a lowering of plasma GH and IGF-1 concentration through the stimulation of somatostatin.
Uncoupling proteins are proteins that can uncouple ATP production from mitochondrial respiration, by causing a proton leakage, leading to the dissipation of energy as heat. Although certain uncoupling proteins have been shown to influence variations in metabolic efficiency and thermogenesis, the role of UCP2 in energy balance is currently unclear. Nevertheless, UCP2 has been shown to regulate insulin secretion, and it is up-regulated by a high-fat diet, suggesting UCP2 to be important for determining basal metabolic rate and possibly resistance to obesity. Most importantly, significant genetic linkage has been established between microsatellite markers encompassing the location of UCP2 with resting metabolic rate, body mass, body fatness and fat mass in humans.
It remains advantageous to provide further SNPs that may more accurately predict the meat quality phenotype of an animal and also a business method that provides for increased production efficiencies in livestock cattle, as well as providing access to various records of the animals and allows comparisons with expected or desired goals with regard to the quality and quantity of animals produced.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.